Inlaying one material into another material has been an art in many countries for centuries. Typically, in such inlay art, an excavated inlay pattern is cut in an inlay base, such as a table top or the like, and a matching inlay relief product, usually of a different colour and often of a different material, is cut to coincide with the excavated inlay pattern in the inlay base. The cut relief inlay is then inserted in the engraved inlay pattern in the inlay base. Over the centuries, this inlay art has been highly labour intensive and has required a high degree of painstaking skill from the artisan. To reduce the labour intensity and the level of skill involved, and to improve production rates, a number of techniques have been developed over the years to facilitate the inlay engraving and inlay process.
The following U.S. patents disclose inventions and techniques for forming inlays in wood and other materials.
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 3,649,806 Konig Mar. 14, 1972 4,126,500 Palanos Nov. 21, 1978 4,139,409 Macken et al. Feb. 13, 1979 4,486,371 Caliri Dec. 4, 1984 5,284,536 Gruber Feb. 8, 1994 ______________________________________
Palanos discloses a system of making positive and negative forms of an image on two materials and then juxtaposing those two materials together to construct an inlay of one material in the other. Subsequently, the base of the inlay material is sanded or ground away to expose the inlay. Both wood inlays and metal inlays are disclosed. Palanos does not, however, disclose any apparatus for practising his inlay method using laser engraving technique.
Specifically, Palanos uses a laser to selectively form patterns in two pieces of material by vaporizing unwanted portions thereof. One piece of material has the negative pattern of the other piece of material. The patterns do not completely penetrate the thickness of the pieces. A suitable adhesive is applied to the two pieces of material and they are then mated together so that the raised non-vaporized area of one piece mates with the vaporized area of the other piece. When the adhesive is set, one surface is sanded or planed until the thickness of the two joined pieces is reduced to reveal the area where the two pieces have been mated.
Macken et al. disclose a method for forming a raised metallic relief involving a metal foil sheet affixed to a support film which is selectively etched. The film is affixed to a wood surface and then exposed to a laser beam to vaporize the support film and wood in areas unprotected by the metal foil sheet.
A major longstanding problem in the inlay art is the competing objectives of having the edges of the inlay coincide as closely as possible with the edges of the inlay base, so that the margin between the inlay and the inlay base is as thin as possible, balanced with leaving sufficient space in the margin, and under the inlay, to permit the presence of an adhesive which binds the inlay and the inlay base together.
Another major longstanding problem has been the difficulty usually involved in getting the inlay to penetrate readily into the inlay base. Often, particularly with complex inlay patterns, the outline of the inlay does not precisely match the outline of the excavated area in the inlay base. Thus a considerable amount of trial and error is required in fitting the two pieces together. This procedure often results in the inlay splitting or breaking, or the edges of the inlay, or the edges of the engraved area in the inlay base, becoming chipped, frayed, or damaged. In such cases, the inlay is of lower quality, or the inlay and/or the inlay base must be discarded and a new inlay and or inlay base cut.
A further longstanding problem is the difficulty experienced in having the inlay penetrate to a consistent depth in the engraved area of the inlay base. In many situations, for example, with a wood inlay of attractive hardwood(s), the grain pattern of the inlay hardwood is highly important to the overall attractiveness of the inlay wood product. If the inlay is not of a consistent depth, and a portion of the wood inlay is subsequently sanded away, an uneven or unattractive "wave-like" appearance can result in the grain of the inlay wood. In many cases, this "wave-like" appearance in the grain is undesirable. To avoid the appearance of a "wave-like" pattern in the wood grain of the inlay material, it is important that the depth of the wood inlay material in the wood base is consistent over the entire engraved area of the wood base. In that way, subsequent sanding of the wood inlay product cuts a consistent plane across the entire surface of the wood inlay product and reveals a consistent "wave-free" grain pattern.
A further problem inherent in to inlay products and engraved areas in wood inlay bases using a laser is that the laser usually leaves a small charred area along the margin between the inlay and the inlay base. This charred margin is unsightly. Furthermore, the charred margin prevents good adhesion between the adhesive interface between the inlay and the inlay base.
Yet a further problem in the inlay art is the difficulty inherent in doing multiple laser inlays of different woods or materials in one design without spoiling the previous inlays.
To date, laser inlay processes have been slow and uneconomical. Laser inlay has been done in the past by several methods:
Laser cutting veneers and individually placing the veneers in the excavated inlay. This process is slow and expensive. PA1 Defining an inlay pattern on a piece of material, and a negative pattern on another piece of material, engraving one pattern and embossing the other, then mating the materials together and sanding down the backing to expose the inlay. This process usually involves carefully enlarging the engraved pattern to allow the embossed image to fit. While it is possible to produce intricate inlays in this way, the process is slow and cannot be used in an economical high production process. PA1 The use of wood and metal is another variation of laser inlay process where the inlay is affixed to a metal plate, and the wood engraved out with a pattern. An embossed composite of the pattern is then joined to the inlay and the plate removed. This process, too, is slow and difficult.